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The Squamata, a vertebrate group that includes ` lizards’, amphisbaenians and snakes, have inhabited Patagonia since the Late Cretaceous. The Mesozoic record comprises an iguanian, a scleroglossan and a great diversity of snakes that include, among others, the most primitive terrestrial forms. Snakes were also well diversified in the Palaeogene, with fossils of madtsoiids and boids (including the oldest record of the extant Boa) found as far south as 46 S, following the then dominant subtropical conditions in the region. The Palaeogene record comprises small, medium-sized and large forms. The only boids that persisted at the beginning of the Neogene are all small forms, suggesting colder temperatures than during the Palaeogene. The oldest South American ` colubrids’ made their first appearance at this time, reaching latitudes south of the current Patagonian distribution (50 S). The Neogene record also includes the first occurrence of extant iguanians (Pristidactylus and Liolaemus) and teiids (Tupinambis). The latter reached the southernmost distribution of its evolutionary history during the Miocene. The distribution of boids, ` colubrids’ and tupinambine teiids at higher latitudes than at present indicates warmer conditions during the Miocene. The uplift of the Patagonian Andes, followed by a decrease in temperature and an increase in desertification, induced a strong contraction in the distribution of tupinambine teiids to northern regions of Patagonia and even forced the complete disappearance of boids from this region. In contrast, these changes appear to have favoured the diversification of iguanian genera on both sides of the Patagonian Andes. (C) 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 441-457.